Abstract

ROJAS-RUIZ, Norma E.; VAZQUEZ-CRUZ, Candelario; SANCHEZ-ALONSO, Patricia  and  SANSINENEA-ROYANO, Estibaliz. Population analysis of Bacillus thuringiensis interaction in vitro with soil bacteria. Agrociencia [online]. 2010, vol.44, n.8, pp.941-953. ISSN 2521-9766.

The bacteria Bacillus thuringiensis is used as a biological insecticide in agriculture, but little is known about its persistence in the soil. The objective of this study was to analyze the interaction of the vegetative, or non-sporulated, cells of B. thuringiensis, with 11 native soil microorganisms. The bacteria were confronted by paired co-culture under controlled conditions, and growth kinetics of the studied microorganisms was evaluated by cell count on plates. The results showed that the development of B. thuringiensis is affected by seven of the 11 soil microorganisms. Of these antagonists, Pseudomonas fluorescens was one of those that most reduced the population of B. thuringiensis vegetative cells at 28 °C but not at 37 °C. This suggests a possible mechanism of thermoregulation in the antagonism. The antagonistic effect of P. fluorescens was also observed on other soil B. thuringiensis strains isolated during this study, even in medium that was free of P. fluorescens cells, indicating B. thuringiensis susceptibility to antibacterial substances of P. fluorescens. This suggests that the soil is not an environment that favors the multiplication of B. thuringiensis cells because of possible microbial antagonism.

Keywords : Microbial antagonism; Pseudomonas fluorescens; Klebsiella pneumoniae.